function Is() {
      agent  = navigator.userAgent.toLowerCase();
      this.major = parseInt(navigator.appVersion);
      this.minor = parseFloat(navigator.appVersion);
      this.ns    = ((agent.indexOf('mozilla')   !=   -1) && ((agent.indexOf('spoofer')   ==   -1) && (agent.indexOf('compatible') ==   -1)));
      this.ns4   = (this.ns && (this.major      ==    4));
      this.ns6   = (this.ns && (this.major      >=    5));
      this.ie    = (agent.indexOf("msie")       !=   -1);
      this.ie3   = (this.ie && (this.major      < 4));
      this.ie4   = (this.ie && (this.major      ==    4) && (agent.indexOf("msie 5.0")   ==   -1));
      this.ie5   = (this.ie && (this.major      ==    4) && (agent.indexOf("msie 5.0")   !=   -1));
      this.ie55  = (this.ie && (this.major      ==    4) && (agent.indexOf("msie 5.5")   !=   -1));
      this.ie6  = (this.ie && (agent.indexOf("msie 6.0")!=-1) );
    }

    var is = new Is();